1. Field of the Invention
The invention herein pertains to the field of herbicides. More particularly, the field of this invention pertains to the use of bis-(3,5-dicarboxylic)esters of tetrahydropyrans and piperidines as preemergent herbicides.
2. Description of the Prior Art
Bis(2,6-trifluoromethyl)-3,5-dicarboxylic acid esters of tetrahydropyrans and piperidines are known. Baldev Singh et al published a report of their investigation in the Journal of Heterocyclic Chemistry, Vol. 17, 1109 (1980) wherein they describe the reaction of ethyl 4,4,4-trifluoroacetoacetate with aryladehydes and aqueous ammonia in ethanol. They dissolved that such a reaction, previously reported by Balicki et al, Chem Abstracts, Vol. 82, 72739P (1975) produced diethyl 4-aryl-2,6-dihydroxy-2,6-bis-(trifluoromethyl)-3,5-piperidinedicarboxylate s instead of diethyl 4-aryl-1,4-dihydro-2,6-bis(trifluoromethyl)-3,5-pyridinedicarboxylates. Stereo isomers of the reported piperidinedicarboxylates was also reported as being uncertain. No use was given for the compounds.
The Journal of Organic Chemistry, Vol. 30, pages 3237-3239, September, 1965, contains a report by Dey et al on the synthesis of fluorine-containing tetrahydropyrans. By the process for reacting ethyl trifluoroacetoacetate with various aliphatic and aromatic aldehydes using the usual Knoevenagel conditions provided various 4-substituted compounds. Condensation of ethyl trifluoroacetoacetate with aldehydes was carried out in the presence of both piperidine and potassium fluoride in two different methods to provide the compounds of interest. Compounds substituted in the 4-position by methyl, ethyl, phenyl, p-fluorophenyl and p-methoxyphenyl were reported on the 3,5-dicarbethoxy-2,6-dihydroxy-2,6-bis(trifluoromethyl)tetrahydropyran molecule. No use was given for the compound, nor are branched-chain alkyl substituents disclosed in the 4-position.
In U.S. Pat. No. 3,700,695 to Carr et al, there is disclosed compounds having the following general formula ##STR2## wherein n is from 0 to 1, wherein one of the R's is selected from the group consisting of fluorine, alkyl, cycloalkyl, aryl, perfluoroalkyl, perfluorocycloalkyl, and perfluoroaryl, wherein another one of the R's may be selected from the group consisting of alkyl and perfluoroalkyl, wherein the remaining R's are selected from the group consisting of hydrogen and fluorine, provided that at least one of the R's contains fluorine or is fluorine, s is a number from 1 to 3 inclusive, and M is substance selected from the group consisting of fluorine, chlorine, bromine, iodine, cyano, alkylcarbonyloxy, arylcarbonyloxy, cycloalkylcarbonyloxy, alkylsulfonyloxy, cycloalkylsulfonyloxy, arylsulfonyloxy, phosphinylidynetrioxy, phosphinidynetrioxy, alkoxyphosphinidenedioxy, dialkoxyphosphinoxy, aryloxyphosphinidenedioxy, diaryloxyphosphinoxy, alkylphosphinylidenedioxy, arylphosphinylidenedioxy, sulfonyl and sulfinyl. The preparation of these compounds and their uses in improving the clarity of plastic films and as herbicides are also described. As is indicated by the above formula, fluorine substitution in these compounds occurs on the ring directly or the ring may be substituted by perfluoroalkyl radicals. Certain of these compounds are reported to have herbicidal activity while the majority of compounds were utilized in polyvinyl chloride films as clarifiers. The herbicidally-active compounds generally were ring substituted fluorine-containing compounds having a carbonyloxy or sulfonyloxy radical in the 2-position of the pyran ring. Pre-emergent herbicidal activity of such compounds is noted with respect to rice, millet and cucumber.
While, as will be apparent from the above, the compositions of this invention have been noted in the prior art, none of the prior art discloses or suggests the utility of the dicarboxylate esters as pre-emergent herbicides nor is there disclosed the novel process of the present invention for preparing such compounds.